1. Field of the Invention
The present invention relates to a throttle valve controller for an internal combustion engine, which transmits the revolution of a motor in accordance with the operation amount of an accelerator to the valve shaft of a throttle valve for controlling the amount of intake air for an internal combustion engine by means of a gear mechanism consisting of a sun gear, an internal tooth type gear ring and an epicyclic gear to be engaged with these gears.
2. Description of the Prior Art
FIG. 7 is a partially cutaway side view of a conventional throttle valve controller for an internal combustion engine. In FIG. 7, reference numeral 1 denotes an internal combustion engine, 2 a throttle valve, 3 a valve housing for the throttle valve 2, 4 an inlet passage for the valve housing 3, 5 a valve shaft rotatably attached to the valve housing 3 and extending through the inlet passage 4, 6 a valve body attached to the valve shaft 5, 7 an inlet pipe such as an inlet manifold for connecting the inlet passage 4 to an unshown inlet hole in the internal combustion engine 1, 8 a motor such as a DC brushless motor located adjacent to the throttle valve 2, 9 a motor housing for the motor 8, 10 a stator built in the motor housing 9, 11 a rotor to be paired with the stator 10, 12 an output shaft fitted with the rotor 11, 13 a bearing for rotatably connecting one end of the output shaft 12 to the motor housing 9, and 14 a terminal connected to the coil of the stator 10 and built in the motor housing 9. The motor 8 and the throttle valve 2 are located adjacent to each other in such a manner that the revolution center of the output shaft 12 and the revolution center of the valve shaft 5 are concentric to each other and located on a straight line L1 shown by a one-dotted chain line, the other end of the output shaft 12 and one end of the valve shaft 5 are opposed to each other with space therebetween, and the end face of the opening of the motor housing 9 formed annular around the other end of the output shaft 12 and the end face of the opening of the valve housing 3 formed annular around one end of the valve shaft 5 are arranged to face each other. While this throttle valve 2 and the motor 8 are located adjacent to each other, the gear mechanism 16 is placed in internal space 15 formed hermetically by the valve housing 3 and the motor housing 9. The gear mechanism 16 consists of a sun gear 17, an internal tooth type ring gear 18 and an epicyclic gear 19 to be engaged with these gears 17 and 18. The sun gear 17 revolves together with the output shaft 12 of the motor 2, and the revolution center of the sun gear 17 and the revolution center of the valve shaft are opposed and concentric to each other. The tooth portion 18a of the ring gear 18 is arranged around the sun gear 17 concentrically, and the center hole portion 18b of the ring gear 18 is connected to the output shaft 12 through the bearing 20 concentrically and rotatably. The ring gear 18 is fixed in the valve housing 2 and the motor housing 9 in such a manner that the outer peripheral surface 18c on the tooth portion 18a side of the ring gear 18 is in contact with the inner peripheral surface 3a of the valve housing 3 and the inner peripheral surface 9a of the motor housing 9 both of which form internal space 15. The revolution center of the epicyclic gear 19 is connected to a support body 21 fixed to one end of the valve shaft 5 through a support shaft 22 so that it can revolve together with the valve shaft 5. After the gear mechanism 16 is placed in the internal space 15, the valve housing 3 and the motor housing 9 are connected to each other by fixing tools such as unshown bolts. Reference numeral 23 denotes a control unit for supplying power to the terminal 14 of the motor 8, 24 an accelerator, and 25 an accelerator sensor for detecting the operation amount of the accelerator 24, converting the detected amount into an electric signal, and outputting the electric signal to the control unit 23. A structure similar to this prior art is disclosed by Examined Japanese Patent Publication No. 6-65854.
A description is given of this throttle valve controller. When the accelerator 24 is operated, the accelerator sensor 25 which has detected the operation amount of the accelerator 4 outputs an electric signal to the control unit 23 which in turn supplies power in accordance with the electric signal from the accelerator sensor 25 to the terminal 14 of the motor 8. The stator 10 generates a revolution magnetic field in accordance with power running in the coil of the stator 10 from the terminal 14. The output shaft 12 revolves by attraction and repulsion caused by the revolution magnetic field generated by the stator 10 and the magnetic field of the rotor 11, and the sun gear 17 revolves together with the output shaft 12. The epicyclic gear 19 revolves around the sun gear 17 and on the support shaft 22. The valve shaft 5 is revolved by the revolution of this epicyclic gear 19 through the support body 21. By this revolution of the valve body 6, the cross section of the inlet passage 4 is controlled. That is, the gear mechanism consisting of the sun gear 17, the ring gear 18 and the epicyclic gear 19 transmits the revolution of the motor 2 in accordance with the operation amount of the accelerator 24 to the valve shaft 5 of the throttle valve 2 for controlling the amount of intake air for the internal combustion engine 1 through the support body 21.
In the above throttle valve controller of the prior art, after the whole shape of the ring gear 18 including the tooth portion 18a, the center hole portion 18b and the outer peripheral surface 18c is formed by cold forging, the hole wall surface of the center hole portion 18b is finished by machining for engagement between the ring gear 18 and the bearing 20, and the outer peripheral surface 18c is finished by machining for engagement between the ring gear 18 and the inner peripheral surfaces 3a and 9a. Therefore, there is a limit in reducing the production cost.